Leaching process



Nov. 6, 1928.

i u;' l

R. F; GRANT ET AL LEACHING PROCESS Filed March 31, 1925 2 Sheets-Sheet -l Franklin B. Richards Richard F. Grant Herbert E. T Vfizerbee INVENTORS Patented Nov. 6, 1928.

UNITED, STATES PATENT OFFICE.

RICHARD r. enmtr, FRAN LIN 1B. nrenanbsnnn nnnnnnr n. wn'rnnnnnnjor CLEVELAND, OHIO, assrenons oronn-rounrn re nownnn M, Hanna, or CLEVE- LAND, 01110.

LEACHING PROCESS.

Application filed Mare-h 31, 1925. Serial no} 19,684.

Our invention relates to improvements in a chemical leaching process and morepar ticularly to the leaching of a valuable mineral content from ore depos'ts m their nat ural and undisturbed position; the object.

of said invention being to obtain the min eral values at aniinimum costand without incurring the expense of usual mining operations.

Leaching processes practiced under ordinary conditions, necessitate mining and more or less minutely sub-dividing the treated ore, because of the necessity for abbreviating the treating period together with the construction of enormous tanks or containers and their equipment with suitable auxiliary apparatus;

It is quite obvious, accordingly,'that if the ore values may be recovered in sufficient quantities without incurring such heavy overhead expense, very much lower grade ores may be leached successfully, or a much lower cost of production may be obtained with ores of the same characteristics. ing these requirements in view, we have devised a process for treating many mineral bearing formations in place, i. e., in their natural and undisturbed position, and with a minimum expenditure for instituting the leaching operations.

Thus, withmineral bearing formations of more or less pervious character, either due to the character of the formation itself, or'

to minute fissuresand fracturestherein, it is possible to obtain the deferred percola= tion of a chemically active leaching fluid and the collection of such leaching fluid with its dissolved content, either by tunneling, sinking shafts, runningdrifts and col lecting through the naturalfiow, or pumping the surface water from the surrounding treated area, together with the leaching fluid and its mineralcontent.

Although We recognize thatmineral bearing formationsw'ill present their own individual problems, we shall explain and illus trate two typical workings for leaching ore values in place, in order to set forth the principles of our invention. WVe may make reference to the accompanying drawings wherein, Fig. 1 is a diagrammatic view, in cross section, illustrating the principle that the level of the ground water roughly follows the topography of the terrain.

Fig. 2 is a similar diagrammatic view,

' Fig. 5.

illustrating the converging depressed flow of the ground water produced by sinking a shaftand pumping therefrom.

Fig. 3 is another diagrammatic view, illustrating the practice of our invention under topographic conditions resembling those shown inFig. 2. V p I Fig. 4 is anotherdiagrammatic view, illustrating the practice of our invention under topographic conditions, avoiding the necessity for pun'iping the ground water and per colating leaching fluid.

Fig. 5 is a diagrammatic plan view of the workings shown in Fig. i, and Fig. 6 is a sinnlar view of the workings shown in Throughout the several figures of. the drawings, we have employed the same charactor of reference to designate similar elements. a i

It is a well known physical fact that the level of' thegroundwater roughly follows the topography of the particular terrain and that the flow of such ground water a, from a higher level Z), to a lower level 0, is not on a straight line but generally follows the paths indicated in Fig. 1. This ground water must be reckoned with in the practice of our invention asunder the conditions assumed in Fig. 2, wherein a shaft (Z is sunk to any desired level, from which the ground water is continuously pumped by pump 0. The How converges on the shaft or its connected workings to collect in a common sump Z at the bottom of the shaft. Thus, it has been found in a typical instance, upon testing bore holes, that the level of the ground water is deflected in an area L00 feet wide by lowering the-water 50 feet below the normal level of the groundwater in a winze connected with undeground workings 70 feet below the normal level of said ground water.

It, therefore, is apparent that water or chemically active solutions introduced into the trenches f, Fig. 3,"dug at a distance from the mouth of the shaft and substantially paralleling the lower workings, indicated in Fig. 5, throughout the area affected by the displaccnient of the ground water, will find their way to the deflected surface of said ground water and flow into the sump as generally indicated by the lines f.

The. under workings, with the conditions assumed, comprise the connecting drifts g, so that the workings will produce a flow tit in theiliiorm liifihnl 'enoinnousLiirohghithat tionlof ferric sulphateior liif i fi'eeteiiid for 55 converges at the bottom of the pump shaft d. .Thexvorkingsof Figfilassume a depressed leyelffoifth ground water. s'ubste'ntihlly coincident iv'ith "the tunnel 'h, from which lateral drifts h, are run beneath thev-area of seepage from the trenches z, contiiining the chemically activetrleachingwfluid. :T he leaching fluid will collect and be drained off: f'romctheidri ftSl': bywthe lJHDIlBlJJM'LfiOI" the 1' recovery of st-he t'amineral :content. iSiich recovery, efecburse; isxdependent -upon2the elniracter/ of: thexclissolvedarninerel "andni ay "Ibezaccomplishsdilr anyowellxlmown manner. x'liherzflowage of =theivater or "chemically reactive solutions from the: surface ,preferably isthroulglrtheinutural joints-'and'crdcks, but istalsorthroirglr the capillary passages in theuorelfonnjation where "itiney comewin -contact "svitlnrhineral particles thatzzmay be disseminated throughout theZ-rock. Inthe units: and cracks: ithe :fiowf follows :the 'ordirnztry law's ofrhydrost'zitics. Inthecapillary passages the rflow is 1n1iclfslowen'andiscontrolled by the viscosityof the liquid, being .ninuch greeted with (solutions of low: viscosity than withsnore-viscous solutions. The viscosity of; rsolutionsrini general ,in much vless at higher than at lower temperatures, therefore,%conditions-.awhichnaturally lend themsellves to higher'temperatures are very? desirab e; I a i a; wItxis; our; purpose, .as indicated :above, to aobtain' thewnatural circulation of irunderground *Wate1*,;-suitably Hcontvolled for any lirgiven situation, soiflas to make; possible-the vleach-ing' 0f 1; more orless --ho nogeneousore i bearing: formation withoutj previous.- mining OPGlfillilOIlSqlOtllGl than those necessary -to control the dflowi l of grounid" Water and. the leachedeontent, -:'l-he --leachi ng preferably is attained wi'tli-siiitable dilute solutions that are chemically T reactive, 2 or suitable. dilute :acids. i'llhe importance of limiting and restricting 2 the: action of the leaching fluid mtothesarea-iend volume of theore body affected by the tunnelling is obvious, for the reason that very asubstantial losses of the mineral bearing fluid otherwise would occur, even to a the extent at making such operations impractical or unprofitable in practice.

As la specific it example of our chemical leaching process, 'we',n1ay1 instance the. remployment' 'in the trenches of a dilute soluthe purpose of dissolving the copper content in chalcocite formation. The ferric sulphate ia'dvantage'ou'slym ay be"used ilrsolu'tioncontaining 2" to 'res cent'there'of andl'its percolation.will dissolve the-coppercontent of 'the"niineral formation as a sulphate with tl1e-red-uction of i the ferric sulphate to ferrous sulphate. The cement co )per may berecovered' from athe2puinped sur ace water and leaching fluid -by treating vwith iron scrapfinthe well known manner, ivl iileuthe xfei-rous sulphate; may he reconvertedi into i -ferric sulphate=to further a cyclic process of leaching. y p a I A i However, eve, do not desire to confine, our

invention to any specific leaching. lfiuid, nor any detailed procedure other thanflthatuout- .-lined1in thesappendedv claim. .Thuspin the ispecificinstence mentioned above by way of illustration, either dilute sulphuric acid. or dilute i'ferricrsulphate one solution of .the latter @with free acid vcontent Uniaylbe ,em-

;ployed *for leaching chalcocitefifof' {vhich --suclt dilute-solutions: are w'ellledapted but other dilute solutions obviouslyl'fshould'lbe continuously isupplied to minerj l i hearing formationsxof-l diilerent is content; andf'characc."teristicsl withinsthe spirit. and. intent v of our invention.

v'Having nowldescribedrtypical procedures for practicingv our invention, wencl'aiin as -,-ne1v, andiidesireto'secure byll'nettersfBetent,

sighs-"following:

y ,The 1 herein I described aoperatio'ns for? in- ;suring the leabhing of copper siidue's lace, whicl1.,consists.in driving, eils'hziftm'lirli con- 'necting rhitts,to ividen operations. at Jziilvel below that of "the surfacefi tvatergproviding localized. trenches, or contiiinerslet' T the surztace ,eppurtennt' suchniidergroun'd' workings, supp lyinga solution of ferric sulphate ofuapproimnzitely "4% .l'dilution above the drifted area of lcopper ore, ,perrnitting" its J continued percolation in quantity "through" the ore body, and punipin "the surface-Water and percola'ting' leaching? uid from the level a of"thedriits. I v testiinony livhereof ,we'ido fnow our signatures.

'RICHABD 'iIGB-ANT. c,

..-ERA1\TKLIN"BZRI'CHABDS. *HERBERT -"WETHERBEE. 

